1. Technical Field
The present invention relates to metering valves, and in particular, to pintle valves, such as can be used to meter liquid or gaseous fuel in air and space vehicles.
2. Description of the Related Art
Valves for metering fuel and other combustible media to engines in aircraft and spacecraft are well known in the art, see e.g., U.S. Pat. No. 6,250,602, assigned to the assignee of the present invention and hereby incorporated by reference as though fully set forth herein. Such valves are used to control the rate at which pressurized fuel, in a liquid or gaseous state, is supplied to inlet orifices in the engine combustion chambers. The valves are relied upon to provide consistent and rapid control of flow rates of fuel at ignition and during sustained operation. Their operation is critical to proper performance of the vehicle. Poor valve operation can result in unstable engine performance and possible failure.
These valves can have movable stem-like valve members, or pintles, aligned with the outlet port of the valve for controlling the rate at which fuel flows to the engine. Pintle type valves are typically less affected by the temperatures and pressures of the fuel passing through the fuel chamber of the valve, due to their contoured head and axial movement parallel to the media.
The pintles are moved between extended and retracted positions by a drive/actuator system, which can be can be a electric, mechanical, hydraulic, pneumatic or combinations thereof. Typical pintle metering valves, such as in the '602 patent, require a separate actuator system for each pintle valves. Thus, in applications requiring metering of multiple flow channels, separate actuators must be used. The numerous actuators add cost, size and weight to the metering system. In some applications, such as air and space vehicles, for example vehicles with supersonic combustion ramjet (“scramjet”) engines, space and weight must be minimized as much as possible, thus making conventional valves undesirable.
Another problem with separate valves or valve channels is flow division deviation, which occurs when the flow through each valve in a multi-valve system is not identical. Slight deviations between the flow volumes or rates of the valves can significantly adversely impact performance in certain applications. For example, it is critical to minimize flow deviation between the valves metering fuel to the multiple zones of the combustion chamber in a scramjet engine.
Yet another problem pertains to pressure fluctuations at the fuel input section being transferred to the combustion side of the system. Such pressure fluctuations in the combustion area can significantly compromise operational stability of the engine, particularly during thrust mode.